The present invention relates generally to semiconductors, and more particularly, to a system and method for applying photoresist in a semiconductor manufacturing process.
Semiconductor processing requires several different processing steps, including applying a photoresist coating on a substrate such as a semiconductor wafer. Traditionally, photoresist which is a fluid material including photo active compounds and solvents, is placed on the wafer and then distributed about the wafer. One common distribution method is to spin the wafer, controlling the thickness of the photoresist by the amount of solvent in the photoresist and the spin rate of the wafer. Once the photoresist is dispensed onto the wafer, the wafer will continue to spin at a controlled speed as the film gradually dry off as a uniform coating. Following the spin, the wafers may receive a soft bake process on a hot plate to drive off most of the solvents. This traditional method wastes a significant amount of photoresist, especially at the spinning step.
U.S. patent application Ser. No. 08/858,004 describes a system and method for making spherical shaped semiconductor devices. In the manufacturing process for producing spherical shaped semiconductor devices, it is even harder to obtain an even layer of photoresist on the substrate. In order to achieve a similar evenness of the photoresist layer on a spherical shaped semiconductor substrate, if using the conventional spinning method, a significantly greater amount of photoresist will be wasted since the rotation of the spherical devices is more complex than the two dimensional wafer. Further, the thickness of the layer will be hard to control from device to device for the same reason.
It is desired to evenly coat photoresist onto a substrate without incurring significant amount of waste.
It is also desired to uniformly apply the photoresist to different shaped substrates, including spherical shaped semiconductor substrates.
It is further desired to be able to increase the controllability for the thickness of the film layer.
What is proposed is a system and method to coat a conventional wafer or a spherical shaped semiconductor substrates or devices with photoresist by utilizing a jet head assembly including one or more jet heads, each having a plurality of dispense nozzles thereon. The positions of these jet heads may be fixed and target objects such as wafers or spherical shaped semiconductor substrates are traveling in one direction and passing in front of the jet heads during the coating process. Multiple control variables such as jet frequency, jet volume, jet velocity, photoresist material viscosity, substrate speed and distance between neighboring substrates can be adjusted to obtain an optimal coating effect. In some embodiments, the proposed system includes a feeder, a jet head assembly, a heat isolator, a dry heating chamber, and a catcher. In addition, unused photoresist may be recycled for future use. The disclosed system and method thus greatly reduce, and in some cases virtually eliminate, the waste of photoresist in the process.